Fingerprints
The Fundamentals
Every human being carries with
him from the cradle to his grave,
certain physical marks which do
not change their character, and by
which he can always be identified
– and that without shade of doubt
or question. These marks are his
signature, his physiological
autograph, so to speak, and this
autograph cannot be
counterfeited, nor can he disguise
it or hide it away, nor can it
become illegible by the wear and
mutations of time.
- Mark Twain – Pudd’n Head Wilson
Works to Know
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Arch
Core
Delta
Fingerprint
Latent fingerprint
Loop
Minutiae
Patent fingerprint
Plastic fingerprint
Ridge pattern
Ten card
Whorl
Why do we have fingerprints?
• Grip better
• Makes
perspiration
easier on hairless
surface
• Improves sense
of touch
Fingerprints
• Impression made by ridge
patterns on the tip of a finger.
• Consists of 98.7% water and
1.3% other substances (amino
acids and salt)
• Ridge characteristics start to
form around 10 weeks
gestation and are fully formed
at 14 weeks. Formation due
to movement or pressure
caused by fetus and mother.
Fingerprint Principles
According to criminal investigators,
fingerprints follow 3 fundamental
principles:
1. A fingerprint is an individual
characteristic; no two people have
been found with the exact same
fingerprint pattern.
a. Determined by ridge patterns called
minutiae
b. Average person has 150 individual
ridge characteristics on 1 print
Fingerprint Principles
2. A fingerprint pattern will remain
unchanged for the life of an individual;
however, the print itself may
change due to permanent scars
and skin diseases.
a. Contains ridges (hills) and
grooves (valleys).
a. Ridges contain pores where
perspiration is discharged. This and
oils picked up from hair or face are
what leaves impressions of prints
behind. (latent prints)
Fingerprint Principles
3. Fingerprints have general characteristic
ridge patterns that allow them to be
systematically identified.
a. ridge characteristics are known as
minutiae: ridge endings, bifurcations,
enclosures, and other ridge details.
b. These ridges are placed into 3 classes.
Fingerprint Classes
There are 3 specific classes for all fingerprints based
upon their visual pattern: arches, loops, and whorls.
Each group is divided into smaller groups
as seen in the lists below.
Arch
Plain arch
Tented arch
Loop
Radial Loop
Ulnar loop
Whorl
Plain whorl
Central pocket whorl
Double loop whorl
Accidentical
Interesting Info
Fingerprint Factoid:
65% of people have loops,
30 - 35% have whorls,
and 5% have arches
Did you know?
Dactyloscopy is the study of fingerprint identification.
Police investigators are experts in collecting
“dactylograms”, otherwise known as fingerprints.
Arches
Arches are the simplest and least common type of fingerprints
that are formed by ridges that enter on one side of the print and
exit on the other. No deltas are present.
Spike or “tent”
Plain Arch
Ridges enter on one side and
exit on the other side.
Tented Arches
Similar to the plain arch,
but has a spike in the center.
Loops
Loops must have one delta and one or more ridges that enter and
leave on the same side. These patterns are named for their positions
related to the radius and ulna bones.
Delta
Ulnar Loop (Right
Thumb)
Loop opens toward
right or the ulna bone.
Radial Loop (Right
Thumb)
Loop opens toward the
left or the radial bone.
NOTE: On the left hand, a loop that opens to the left would be an ulnar
loop, while one that opens to the right would be a radial loop.
Whorls
Whorls have at least one ridge that makes (or tends to make) a
complete circuit. They also have at least two deltas. If a print has
more than two deltas, it is most likely an accidental.
Plain
Whorl
Central
Pocket
Whorl
Draw a line between the two deltas in the plain and central pocket
whorls. If some of the curved ridges touch the line, it is a plain
whorl. If none of the center core touches the line, it is a central
pocket whorl.
Whorls – Part 2
Double Loop Whorl
Accidental Whorl
Delta
Delta
Double loop whorls are
made up of any two loops
combined into one print.
Accidental whorls contain two
or more patterns (not
including the plain arch), or
does not clearly fall under any
of the other categories.
Identify each fingerprint pattern.
Right Hand
Left Hand
Right Hand
Right Hand
Left Hand
It’s time to make
some prints!
Avoid
Partial
Prints
GOOD PRINT
Get as much of the top part
of your finger as possible!
Directions
1st – Roll the “pad” portion of your thumb over the
ink pad from the left side of your thumb to the
right. You do not have to push down really hard!
2nd – Roll the “pad” portion of your thumb from the left side of
your thumb to the right in the correct box on your paper to make a
thumbprint.
3rd – Continue this process to make a fingerprint of all ten fingers
on the “My Prints” worksheet.
4th –Use your notes and a magnifying lens to help you figure out
what type of pattern is found in each of your fingerprints. Label
each one with the pattern’s name.
Find Your Henry – FBI Number
• The first step to classifying fingerprints is to identify the presence of any
whorl patterns.
• A number is assigned based upon what finger the whorl is present.
• Add a 1 to the denominator and numerator to avoid zeros.
Right
Right
Left
Left
Index
Ring
Thumb
Middle
16
8
4
2
Right
Right
Right
Left
Thumb
Middle
Little
Index
16
8
4
2
Add a 1 to the numerator and denominator at the end.
Left
little
1
Left
Ring
1